1. Field of the Invention
The present invention relates to a drum as a percussion instrument, and more particularly, to an improved tightening device for applying tension to a pair of drum heads.
2. Description of the Related Art
Drums for percussion, such as bass drums, snare drums, floor tom-toms, aerial tom-toms, etc., comprise a cylindrical drum shell open at both ends, a pair of drum heads individually covering two opposite end openings of the drum shell, and means for applying tension to the drum heads. The tensioning means includes hoops arranged along the respective edges of the drum heads, tension bolts inserted individually in holes in the hoops, and metal lugs having nuts into which the tension bolts are screwed. The lugs are fixed to the drum shell by means of screws.
Conventional metal lugs can be classified into two types; one-way type and two-way type. In the one-way lugs, the nut mating with the tension bolt is provided only on one side of a lug body. Accordingly, the one-way lugs can apply tension to only one of the drum heads. The lugs of this type can be made relatively compact. In these lugs, however, the lug body is pulled strongly from only one side by the tensile force of the drum head, so that lug mounting portions of the drum shell and the tension bolts are subjected to a great bending stress. Thus, if the drum head is subjected to excessive tension, the lug mounting portions or the tension bolts may possibly be deformed or bent.
On the other hand, the conventional two-way lugs are provided with an elongated lug body extending in the axial direction of the drum shell. The whole lug body is integrally formed by casting. The nut mating with the tension bolt is provided at each end of the lug body. In a drum using the two-way lugs constructed in this manner, the respective edges of the drum heads are simultaneously pulled toward each other by means of the paired tension bolts. In other words, the lug body is subjected to two opposite tensions in the axial direction of the drum shell. Since these reciprocal forces on the lug body are balanced with each other, the lug body can withstand great deal of tension. Thus, the metal lugs of this type are called high-tension lugs.
The body of the high-tension lugs must have a length agreeable to the axial dimension of the drum shell. If the lug body is too short, the distance between itself and each hoop is so long that the lug body and the hoops cannot be connected by means of regular tension bolts. If the lug body is too long, on the other hand, its ends may engage the hoops, so that the drum heads cannot be subjected to tension. Therefore, the lug body must have the length best suited for the axial length of the drum shell. Since the lug bodies are formed by casting, however, production of lug bodies of different lengths requires use of dies of as many types as the lug body types. In consequence, increased types of lug bodies require an increased number of dies, thus entailing an increase in the manufacturing costs of the lug bodies.